The passage of California Proposition 1A (2008) set in motion a complete reconstruction of the railroad between San Jose and San Francisco. This blog exists to discuss compatibility between HSR and Caltrain, integration issues, and the impact on adjoining communities.

31 July 2016

Future Proofing Hillsdale

The next big grade separation project on the peninsula rail corridor will be at 25th Ave in San Mateo, a logical next step in the decades-long process to grade separate the corridor. This grade separation will establish a 6.5-mile stretch of 100% grade separated right of way, laying the groundwork for a future four-track mid-line overtake facility that will allow express trains to overtake slower commuter trains under the "blended system" jointly planned by Caltrain and the HSR authority.

Preliminary rendering of new
Hillsdale station with island platform

The latest plans presented to the Caltrain board of directors show a split-grade elevated solution, built sufficiently wide for four tracks but initially only fitted with two tracks spaced on approximately 48-foot centers. The Hillsdale station is moved north by a quarter mile to straddle 28th Ave, and fitted with a central island platform sized approximately 36 x 700 feet and built 8 inches above the rails.

Vertical circulation to this island platform is provided at the north end (two stairways connecting to the sidewalks on each side of the new 28th Ave underpass) and the south end of the station (a new pedestrian tunnel with one stairway and one wheelchair ramp). In cross section, the new Hillsdale might look like this:

Of course, the accelerated schedule for its completion is closely linked to electrification, so quite soon thereafter it might look like this, with mixed diesel and EMU service. Note that per Caltrain plans, the overhead contact system is 22 feet above the rails. plenty to clear even the tallest freight cars.

It's not too difficult to guess what happens when the blended system overtake tracks are built: the new platform and all associated vertical circulation (stairs and ramp) will be demolished, to be replaced by a pair of new express tracks right down the middle of the corridor. A first phase of this "New New Hillsdale" station would like this, hopefully with level boarding platforms. Note the new portal configuration of the overhead electrification, to span across four tracks and two platforms without placing poles close to the edge of the new platforms:

After demolition of the "New Hillsdale" island platform, the original 48-foot track centers allow for two additional overtake tracks and a central fence (track spacing 15 + 18 + 15 feet) to prevent passengers from crossing between the two new side platforms of the "New New Hillsdale." Including stairs, the "New New" station is 106 feet wide and looks as much as possible like any station on Amtrak's Northeast Corridor. It could almost be mistaken for Princeton Junction:

While it's a fine idea to build the new grade separation sufficiently wide for four tracks, demolishing the "New Hillsdale" station only to replace it so soon with a "New New Hillsdale" seems terribly wasteful. Perhaps this is another case of "why build it right when you can build it twice?" Surely there is a better way.

Rebuilding Hillsdale Once and for All

There's a much better way to build the New Hillsdale once and for all. It initially looks like this:

Note the central island platform is a full-height level boarding platform, disguised for now as an 8-inch platform by raising the track bed by 51 - 8 = 43 inches using a thicker-than-usual layer of ballast. The final footprint of this station, which will ultimately have the HSR overtake tracks on the outside, is less than 100 feet wide at the platform. The footprint will never change; all the concrete has been poured and not another cubic yard is needed in the future. Soon after electrification, mixed EMU and diesel service would look like this:

The overhead contact system is built in its final configuration 22 feet above the eventual height of the tracks; because the tracks are raised by 43 inches, the vertical clearance is temporarily reduced to 18' 5" which still safely accommodates Plate F freight cars, the tallest that have historically been used in this part of the corridor. Therefore, there is no constraint to freight service. This electrification will never change, with all the portals in their final configuration.

When all the diesels are gone and it's time to transition to level boarding, a track maintenance project takes place over a weekend. 43 inches of ballast are removed from under the tracks, using standard track maintenance machines. The rails are never even disconnected. (Not to be too flippant, this is still a major track maintenance operation that would require sophisticated planning and modern high-capacity machinery; but it is certainly within the realm of what Caltrain has done before.) Minor lateral adjustments are made to track and overhead contact system alignment, yielding this for the Monday morning rush:

Not a single cubic yard of concrete is required either to convert to level boarding, or to add the overtake tracks once HSR service begins on the peninsula. The final blended system configuration is ultimately this:

Built once, and built right!

That FSSF Thing

Placing the express overtake tracks on the outside, in a fast-slow-slow-fast or FSSF configuration, as opposed to the traditional slow-fast-fast-slow or SFFS configuration inspired by road design, is a key architectural decision for the blended system. The forces of traditionalism will argue strongly for SFFS because that's how it's "always" done, yielding nice straight express tracks down the middle of the corridor-- but clear exceptions to this "rule" exist, with examples of FSSF corridors in these videos from Sweden (with 125 mph express trains!) and Australia.

The fatal operational flaw of traditional SFFS corridors is that when a track must be taken out of service, either accidentally or intentionally for maintenance, commuter trains either must cut across the express tracks (fouling express traffic) to reach the opposite platform, or use super awkward bridge plates to board from the fouled express track. In contrast, an FSSF island platform is operationally flexible: the train simply crosses over to the opposite side of the island, without ever getting in the way of express traffic. For the peninsula "blended system" where Caltrain and HSR share the corridor, the operational headaches of SFFS could prove unworkable in the long run as the rail corridor is maintained.

One argument systematically trotted out against FSSF is this: wowing express trains around the outside of every island platform will make for a slalom "barf ride" that will give HSR passengers motion sickness, if not downright whiplash. This argument intuitively rings true, but turns out to be patently false when you run the numbers. In reality, an express train blasting around the Hillsdale island platform at 125 mph will do so on curves with a radius greater than four miles, requiring just 2 inches of superelevation to be rendered imperceptible to passengers.

Another argument leveled against FSSF is that the island platform arrangement requires additional right of way compared to a traditional SFFS outside platform arrangement. The footprint of a FSSF station can be made nearly as compact as a SFFS station, especially if the central island platform (shown in the above diagrams at 33 feet wide) is slightly tapered at its ends, yielding an imperceptibly curved platform that is for all practical engineering purposes the same thing as a tangent (straight) platform. In any case, the available right of way at the Hillsdale location is a generous 150 feet wide, making such footprint considerations moot.

The Takeaways

DON'T rebuilt infrastructure multiple times.

DO build it once and build it right, in its final configuration

DON'T build station platforms that are not compatible with level boarding, where this can be avoided.

DO create the Caltrain engineering standards for level boarding.

DO build the new Hillsdale station with a level boarding platform, years before the transition to level boarding occurs, by temporarily raising the track bed to make the platform only 8" tall.

DO build the new Hillsdale station as an island platform, even after high-speed overtake tracks are added

DO put the high speed tracks on the outside, in the FSSF configuration, for operational flexibility.

54 comments:

Would the extra weight of the piled-up ballast cause issues for the bridge? IE would beefing it up add sufficiently to the cost to make it more expensive than rebuilding the platforms? Or require a larger substructure making it difficult enough to get enough clearance below?

Good question, and one I hadn't considered. For a 20 m bridge with ~6 m equivalent width of extra ballast per track, the additional dead load comes to about 500 metric tons. That's the weight of four loaded hopper cars: heavy, but not off the charts.

Some rail cutting might be needed as lowering the rail will make the overall route shorter.

Beside that, lowering/raising of track bed can ballast-less tracks. Some temporary support can be built between the final track bed and the rail ties, then use jacks to lower the rail into the final position when needed.

At some point you guys are going to recognize it's a lot quicker, easier, and cheaper to raise the platforms, than lower the track. Those "temporary supports" need to handle the weight of multiple 200 ton UP freight locomotives, they're not going to be swapped out in a weekend.

The platforms could be planned ahead of time such that they can be raised by installing multiple precast 43" high modules. Ramps and stairs just need to match up with the existing ones on the low platforms, elevators would need some minor tweaking. It doesn't need to be done in a single weekend, just warn the passengers ahead of time which doors will open. This is not rocket science.

And how are you dealing with the access to the platforms? "Minor tweaking" translates to quite a bit of work, and, including concrete, it can not be done within a short time. Having half of the train semi accessible may work for a rural line, but not for the highly loaded Caltrain services.

I have seen quite a few platform raising projects, where it went from 25 cm to 55 cm, and all of them took their time.

I do the reverse commute on Caltrain daily from SF, 22nd Street (one of busiest reverse commute stations) is undergoing construction on the southbound side. As a result, part of the platform is currently closed, and the front car of six car trains is not accessible (it's only a mile or two from SF terminal, so no one ever gets off). Passengers cope with added crowding, conductors have to run around and hit the right circuit breakers to keep the doors in the front car from opening, and sometimes forget to reset them in time for the next station. Such is life.

Remember, this is a new construction center platform station. They could design the platform, from the beginning, to be raised using modular pre-cast concrete sections (brought in by rail or truck, not poured on site), such that ramps and stairs will match up. This is not an unknown technique, many other types of structures are designed to be expanded in precisely this fashion. It does requires forethought.

Since we are allegedly getting dual height doors, the platforms could be raised as slowly as one car length at a time. Not a perfect plan, but in my worthless opinion, far more realistic than lowering the tracks 43 inches in one weekend. I'm sure Caltrain will find an even more bizarre and expensive solution.

Marc, you're imagining how things might be done, but aren't done, and can't be done.

Max Wyss has witnessed how it actually IS done (I also took the time to check out any number of Swiss station modernizations in the last 15 years) and the fact is that changing the height of a train platform is not a simple of fast operation.(Nor, for that matter, is the sort of huge ballast undercut and removal that Clem posits a totally simple operation.)

However adjusting track height against a fixed platform has the immense advantage of being a "continuous process" (or is with the sort of modern track maintenance machinery used in first world industrialized democracies, if very rarely hereabouts.) Changing the height of a platform is pretty much the exact opposite. First the platform itself is a very long and quite wide piece of load-bearing, near-seamless (no trip!) civil engineering; secondly it is a platform on which any amount of "clutter" (shelters, signs, seats, fences, TVMs, etc, etc) is firmly affixed, and not in a way that a machine can come by and just hoist it to a new altitude; thirdly because the platform surface has (or should have; they're really fucked about actually thinking about allowing people to efficiently move on and off platforms in this idiotic country) numerous interfaces to the surrounding ground plane, in the form of steps and escalators (as well as the train track!) which are not at all trivial to change quickly and which must be constructed to precise, safe, and strong standards.

In contrast to all that, the track is a bunch of heavy-duty stuff which takes well to being shoved around by heavy machinery, whether that be specialized on-track or stuff like front-end loaders, and has almost no "moving parts".

FWIW I think that an improvement to Clem's suggestion is to cast the final trackbed and direct-affix the final elevation platform tracks when the station is built. Then cover it and pile ballast or whatever on top for the interim. When the time comes to lower the tracks, remove the interim track, excavate down and uncover the new track, and do a short amount of excavating, tamping, and welding to effect the transition.

(FWIW of course I think that the 50 inch "high level" platform business is utterly bullshit and technically insane, and that something in the 500mm to range 760mm is perfect for both long-long-long-future-HSR and for nearer-term-Caltrain and will be proven so in time.)

Richard, I would find your objections more credible if you applied the same sort of logic to Clem's idea as you did to mine. So, let me try to channel you for a moment, minus some of the vitriol. Please start by providing some evidence that 43 inches of ballast is, in any way, a viable technically approach. Second, provide one existing example of modern track maintenance machinery that is, in fact, capable of removing 43 inches of underlying ballast and tamped fill material (since, as I think you'll quickly find, ballast alone can't be anywhere near that deep, for a variety of pesky technical reasons) for the length of the station platform plus the required grades on either side, in any kind of reasonable time frame.

In reality, if they really wanted to lower the tracks, what would likely happen is that they will hire some contractors to rip out about 2000 feet of double track, dig out the ballast, under-ballast, and fill, replace the under-ballast and ballast, then lay the tracks again. Trying to lower the track in place seems to be far beyond normal track maintenance activities. Oh, yes, I suppose there is some unicorn ballast-less structure that someone could design without relying on all that dirt and crap, but it will still be a hell of a lot easier to rip out the track first, rather than play some sort of giant Jenga game.

These sorts of things will not happen in a weekend, or even a few weeks. They could do one track at a time, if there is some way around the angle of repose issue (like long temporary retaining walls), but single-tracking through Hillsdale for weeks or months will destroy peak hour train throughput. Or, do both tracks at once, but given that peak commute trains are now standing room only in both directions passing through Hillsdale, you're talking about running a bus bridge that needs to move at least 10,000 passengers per peak hour between Belmont and Hayward Park (assuming it's still there). Good luck with that.

The easiest thing to do is close new Hillsdale for however long it takes to raise the platform (if it can't be done in sections), and have the trains stop at another nearby station. The corporate shuttles will have to travel a bit farther, the bicyclists will cope, and a few shuttles to the Hillsdale parking lot will cover the rest.

No mention here of the funding. At the next CHSRA board meeting is an item to have the Authority enter into an MOU with the City of San Mateo to provide $84 million in funding for the project. (has anyone seen a draft of this MOU?)

I wonder how the rest of the Cities along the peninsula feel about San Mateo being the only City to get funding at this time for their own local needs (grade separations etc). How did San Mateo get this attempt at priority funding?

The present Business plan has projected funding only to San Jose at the north end. Why in the world should the Authority now approve funding for San Mateo's project? (I'll answer my own question --- they will approve this funding because they have the best political connections to Caltrain and the CHSRA)

Major advantage of center island platforms include:* riders are always on the one & only "correct" platform regardless of train direction* operations flexibility — trains can use either platform face without passenger chaos* better sense of security since all waiting passengers are together — never isolated* no duplication of platform amenities; better, more efficient utilization thereof* space efficiency: riders get a single wider platform with same or lower station width

Completing this project the way Caltrain is proposing would take significant time, because it is such an intentisive project (removing the "old" island platform, building high speed tracks, catenary, and fencing), and as pointed out in this blog, the amount of time actually available to work on the electrification project is not in abundance. Demolition of a platform would require a significant number of incursions into the two main tracks, and with working periods measured in minutes and not hours, this project will take months if not years longer than the scenario proposed here, adding significantly to the budget as well. And with time and money in such short supply, this should not be taken lightly.

Also, the environmental impact of building a platform and tearing it out a few years later from the pollution of diesel emissions from construction equipment, wasted concrete, steel, and water, and wasted money that could be better spent on other projects that reduce carbon emissions instead of add to them should be reason enough to complete this project correctly the first time.

Maximum ballast depth shall generally not exceed 18 inches. Ballast depth outside these limits must be approved by the Caltrain Deputy Director of Engineering. Thicker ballast section resulting in settlement from ballast consolidation increases the maintenance costs due to increase frequency or need for track surfacing. Track structure over embankment is particularly prone to this phenomenon because the ballast is not being contained.

43 inches of ballast sounds like it may be a bit more problematic than 18 inches.

Second, understanding what they're trying to do at Hillsdale is difficult without knowing the intended construction methods and phasing. Based only on the pictures in the presentation, I'm guessing the process will be quite a bit different than the San Bruno separation. In particular, it looks like rather than using shoo-fly tracks on the outside of the ROW and building a wall-contained embankment in the middle, they'll be building two separate aerial structures on the outside of the ROW, while trains continue running down the middle, then move the tracks to the top of the structures and fill or bridge the middle. Why? Who knows? Maybe it has something to do with the intent to 4-track this area, construction constraints, or keeping one of Caltrain's busiest stations open throughout the process. It might be worth asking the Caltrain folks, maybe they'll have a coherent answer.

Good idea, but two issues: 18" is the maximum platform height that works with existing rolling stock (step threshold). Also, this would require an up-front waiver of CPUC GO 26-D, a major political obstacle that will take time to overcome.

"an up-front waiver of CPUC GO 26-D, a major political obstacle that will take time to overcome."

I hate to repeat myself, but CALTRAIN HAS HAD OVER TWENTY YEARS TO OBTAIN A CPUC GO 26-D WAIVER.

It is also NOT a major political obstacle. I talked in person and at some length with the senior staff person of a very very senior and powerful state politician about this very issue in the early years of this century and I was unequivocally assured that "all it takes is for them to pick up the phone and call our office".

The issue with level boarding is that CALTRAIN STAFF DO NOT GIVE A DAMN AND DO NOT DO THEIR JOBS, not that level boarding is difficult or impossible or undesirable or could not have been completely achieved, corridor-wide, over ten years before today.

Q quarter of a billion, and counting, of outright, unambiguous fraud called CBOSS. Not a single phone call to allow level boarding. That's what we're dealing with.

Too bad the 25th Avenue project geometry, track alignment, and location for the future CHSR in the text and blog are largely inaccurate. None of the proposed 25th Avenue Grade Separation track improvements, track centers, or passenger access facilities (including the platform) will be demolished to accommodate the high speed rail whenever that is constructed. Marc is pretty close... two tracks will be built on the west side of the right of way while trains continue to operate on the existing at-grade tracks. Then the lines will be shifted up top to continue 2-track operation. When CHSR is implemented in the future, a similar track configuration will be built on the east side of the right of way (approximately where the existing tracks are now). The result at the station will be track, platform, track, track, platform, track.

@anon: Interesting, so you are saying that the renderings seen at the July Caltrain board meeting and linked in the opening paragraph (showing a four-track-wide retained embankment with two widely spaced tracks on ~50 ft centers, and a single island platform) are no longer reflective of the latest designs?

What about level boarding? Still an afterthought?

This reminds me of San Bruno, where lip service was paid to HSR (claims of curve flattening and early renderings showing four tracks), but what was actually built will have to be largely torn out if we ever want to put four tracks through or convert to level boarding. Whatever could be done wrong was done wrong, so I sure hope the old San Bruno team isn't getting together again to botch Hillsdale.

Fun fact: the Bayshore station configuration as "presented" (meaning you had to show up in person at the JPB Board meeting in San Carlos and leaf through the engineering plans) to the Board and the public had two island platforms with four tracks and a pedestrian underpass. Great! Hey, they might be doing the right thing, just once.

But by the time this was put out to bid it had been magically changed to olde time commuter railroading Pennsylvania Railroad NEC historical compatibility (platform slow fast fast slow platform) and the underpass had been replaced by the fucking insane, infinitely circuitous, inconvenient, massively oversized, sky-high overpass.

The first anybody outside the San Carlos bunker knew that they were doing the wrong thing was when the tracks were laid.

The Bayshore station is built on land that used to be part of San Francisco Bay. It was discovered that the high water table made the construction of an underground underpass much more expensive and difficult than the overhead bridge used instead. By and large, Caltrain prefers pedestrian underpasses since they don't require elevators and handicapped access can be provided by ramps as shown at the San Jose, Santa Clara, Lawrence, Mountain View, California Avenue, University Avenue, and San Mateo stations.

The rendering is consistent with the current design approach, but the sections or interpretation of the future configuration is not consistent with the approach. The proposed grade separation in San Mateo will elevate the tracks on the west side of the track right of way (left side of the rendering). The parking lot (right of the tracks) in the rendering is where the existing tracks are located and where the future elevated CHSR will be constructed. Through this segment in San Mateo, CHSR will not be located outside of the Caltrain proposed tracks since that is outside the right of way.

While not the project objective, the platform can be raised in the future to accommodate level boarding.

Wouldn't F-P-S-S-P-F allow for Caltrain expresses and locals to meet and exchange passengers cross platform without rebuilding? Isn't that a good thing? HSR and Caltrain expresses will still be traveling past platform faces without stopping, so if Hillsdale has two platforms, the second mirrored on the first, what's the concern?

Gosh. Fhotoshop engeineerin, hooray. We can all rely on _that_ to predict reality, just like the Airbus 380-"derivates" with 3, 4, 5, and 6 decks of passenger seating.

Clem< I thought you were the one who posted here that dual-height doors were optional in the RFP? And that therefore Caltrain hadn't really committed to dual-height? Are you now taking Photoshopped images as superseding that analysis?

It's not a "photoshopped" image as I have periodically featured on this blog. This is a ray trace of an accurate 3D model produced by Stadler.

While the livery could use some improvement, the shape and dimensions are probably quite accurate. What's interesting about it to me is the flat sides: this is unlike any of the other KISS versions and shows that the extruded and welded aluminum construction affords a lot of design flexibility for the car shell. So much for the idea that Caltrain would end up with some diminutive European train: this is clearly a full-size American EMU.

@Clem: From what I have seen with Stadler orders from Switzerland, there can be differences between the picture presented at the signing of the contract and the final product. However, when Swiss customers order, the vehicle is not fully designed and finalized into the last detail (this is often the case with the front, which may actually have to be modified with changes of the regulations, and most certainly with the final livery, which can be changed until the vehicle gets its coats of paint…).

I guess the cross section of the carbody is quite close to the one of the AeroExpress trains.

@unknown: I don't know whether they are using standard couplers between the cars of the train, or a special short coupler (Clem may have an answer for that). KISSes normally have regular diaphragms and standard passways with doors between the cars.

The thing that bothers me is a little further down the way at each of the new grade separations. Have you seen any indication that these will be built wide enough for four tracks from the start or in phases? Or does Caltrain wish to revisit this construction project several years after "completion" and do it all again?

And a further question- how wide do the bridges need to be to allow tracks in a FSSF configuration assuming there is a curve around an island platform? I imagine it is wider than it would otherwise be for optimal placement.